Research On Control Of Seven-Level Cascaded H-bridge Inverter Based On DSP And FPGA

With the persistent development of high power self-turn-off devices and intelligent high-speed microcontroller, high power electronic converter equipments is increasingly deep studied. Multilevel inverter makes a high power and high performance voltage source inverter possible. Therefore, it is very important to study and design control strategies of multilevel inverter both in the theory and in the practical application.In this paper, we discussed different topology and PWM modulation methods of multilevel voltage source inverters. Because of common microcontroller could not provide sufficient PWM pulses for multilevel inverters, this paper presents a DSP+FPGA method to generate enough PWM pulses for need of control seven-level Cascaded H-bridge inverter. First, it produce 6 basic PWM pulses by TMS320LF DSP with a method of asymmetry sampling apply on phase-shift PWM; then FPGA extend those 6 basic PWM pulses to 36 PWM pulses for system needed through sequential control. The method could simplify circuit design, guarantee reliability of system and concurrent triggering of power devices.On the basis of theoretic analysis and simulation study, a prototype of DSP+FPGA PWM pulses generator is realized. The system experiment is performed and the experimental result is given. Experiment result shows the experimental waves and simulated waves are very close, DSP+FPGA PWM pulses generator do a good job.